The overall aim of this project is to elucidate the pathogenesis of neonatal hypoglycemia. Previous work had indicated that new born infants are susceptible to the development of hypoglycemia during fasts because of limited capacities for both ketone synthesis and gluconeogensis. In the past year, studies of small-for-gestational-age infants indicated that higher levels of plasma glucose were maintained when fasting stress was minimized by starting feedings within two hours after delivery. These observations raise serious questions about the current practice of assuming that the low levels of blood glucose found in surveys of neonates fasted for prolonged periods are physiologically normal. In the proposed studies, the response of plasma glucose to early feeding will be further explored in term appropriate-for-gestational-age neonates. In addition, studies will be carried out to further define the limitation in capacity for ketogenesis after birth.